Background/AimFrondoside A is a sea cucumber extract which is well known for its anti‐inflammatory and immunomodulatory properties. The purpose of this study was to evaluate the effect of Frondoside A application in the alveolar socket on inflammatory responses after delayed replantation in rat teeth.Materials and MethodsHuman periodontal ligament cells were cultured and exposed to Frondoside A. Cell‐counting kit‐8 assay was performed to evaluate the cell viability and nitric oxide assay was performed to assess the anti‐inflammatory effect of Frondoside A. Molars were extracted from 32 Sprague–Dawley rats and randomly divided into control and Frondoside A groups. After 30 min of extra‐oral dry time, molars were replanted. In the Frondoside A group, Frondoside A solution was applied in the alveolar socket before replantation. The animals were sacrificed after 28 days and histologically and immunohistochemically evaluated.Results0.5 μM Frondoside A showed higher cellular viability at 6 h and lower production of nitric oxide compared with other Frondoside A solutions (p < .05). The Frondoside A group demonstrated lower inflammatory resorption scores in both middle 1/3 and apical 1/3 of root compared to the control group (p < .05). The Frondoside A group showed lower levels of expression in both cathepsin K and CD45 compared with the control group (p < .05).ConclusionsWithin the limits of this study, intra‐alveolar delivery of Frondoside A alleviates inflammatory root resorption in delayed replantation of rat teeth.